Definition: In this task, you are given an input list A comprising of numbers and alphabets. You need to extract and sort the unique alphabets in the list. The alphabets in the input list will only be in lowercase. Return -1 if there is no alphabet in the input list.
Input: ['9307', 'y', 'z', 'v', 'w', 'l', 'n', 'p', '5513']

l, n, p, v, w, y, z